Add Hash#values.compact vs select benchmark for non-nil values#236
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etagwerker wants to merge 1 commit into
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Add Hash#values.compact vs select benchmark for non-nil values#236etagwerker wants to merge 1 commit into
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Builds on the idea from #124 (sFrenkie), comparing three ways to collect the non-nil values of a hash: - Hash#select { |_k, v| v }.values - Hash#values.select { |v| v } - Hash#values.compact Uses data that actually contains nil values so all three return the same result, plus an equivalence guard, making it a fair comparison. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Pull request overview
This PR adds a new Hash performance benchmark to fairly compare three equivalent ways of collecting non-nil hash values, and documents the results in the README’s Hash section.
Changes:
- Added a new benchmark script comparing
Hash#select.values,Hash#values.select, andHash#values.compactfor filteringnilvalues. - Added a new README entry describing the tradeoffs and including sample benchmark output.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.
| File | Description |
|---|---|
| README.md | Adds a Hash section entry documenting the benchmark and explaining why values.compact is fastest. |
| code/hash/select-values-vs-values-select-vs-values-compact.rb | Introduces the benchmark implementation plus an equivalence guard to ensure fair comparison. |
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| def select_values | ||
| HASH.select { |_k, v| v }.values | ||
| end |
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| def values_select | ||
| HASH.values.select { |v| v } | ||
| end |
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| # Sanity check: all three must return the same values. | ||
| raise "not equivalent" unless select_values.sort == values_select.sort && | ||
| values_select.sort == values_compact.sort |
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| > To collect the non-nil values of a hash, `Hash#select { |_k, v| v }.values` allocates an intermediate hash before extracting its values; <br> | ||
| > `Hash#values.select { |v| v }` skips the intermediate hash but still runs a block per element; <br> |
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What
Adds a Hash benchmark comparing three ways to collect the non-nil values of a hash:
Hash#select { |_k, v| v }.valuesHash#values.select { |v| v }Hash#values.compactHash#values.compactwins by a wide margin (~16x faster thanvalues.select).Why a new PR instead of #124
This builds on the idea from #124 by @sFrenkie, but that benchmark's three expressions aren't equivalent: its test data uses boolean values (
v < 0.5→true/false) and contains nonilvalues. Socompactfiltered nothing while the twoselectvariants also droppedfalse. The "fastest" result came fromcompactdoing less work, not from a fair comparison.This version fixes that:
nilvalues (k < 0.5 ? k : nil), so all three expressions return the same result.key_fast/key_slow) instead ofslow/fast/fastest.Output
README entry added in the Hash section.
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